1. Field of the Invention
The present invention relates to lids, caps other closures for jars, bottles and containers of various types as are used for storing foods under subatmospheric pressure, such as, for example, those having screw or twist off closures.
2. Description of Related Art
Anyone who regularly uses food items stored in jars, bottles or other containers which have been vacuum-sealed has, at one time or another, experienced the frustration of trying to remove the lid, cap or other closure by twisting or prying it against the holding force of the subatmospheric pressure under which the food has been packed. The marketplace is full of implements designed to enable a consumer to obtain greater leverage or obtain a more secure grip on the closure to facilitate its removal. Likewise, numerous home remedies have been devised of the years, such as running the closure under hot water, banging it on a counter top, and the like. Nonetheless, none of these techniques provide a simple, fool proof, quick and easy solution to removal of a closure that acts like it has been welded in place, simply due to effect of the very low pressure that exists within the container.
Of course, containers are well known that have reclosable openings which serve for pressure equalization. For example, containers with pour spouts for dispensing liquid contents of the container, such as gasoline cans, have an opening intended to be located at a high point of the container during pour for the purpose of allowing air to be drawn into the container as its contents are poured out to prevent creation of a vacuum in the container which would affect dispensing of the liquid through the spout. Such an opening usually has a snap-on cap which serves to prevent evaporation of the gasoline when the container is not in use and is designed to pop-off if, due to high temperatures in the storage location, pressure within the container reaches a dangerously high level because of the volatile nature of the contents. However, such pressure equalization openings are not directly applicable to vacuum-packed, food storage containers for various reasons related to the manner in which food packages are stored and displayed, government safety regulations, consumer confidence issues and the like.
On the other hand, attempts have been made to apply such a pressure equalization concept to vacuum-packed food storage containers, for example, by the use of a modified form of the type of pop-top container pull tab to open a vent hole punched in the top wall of the container. Such vented closure caps are described in U.S. Pat. No. 3,850,330 and a form of such a closure cap in which a tamper indicator has been incorporated can be found in U.S. Pat. No. 4,960,206. However, these types of complex vent arrangements have never found commercial acceptance, presumably because of the fact that they are costly to implement, require significant changes to the container and the manner in which it is produced and packaged, are not universally applicable. Still further, these arrangements neither address the problem of spoilage of the unused product if the container cannot be fully reclosed, nor do they provide the consumer with the immediate and familiar tamper indicating button which is currently a standard feature on virtually all vacuum-sealed jars.
Thus, a need exists for a closure for vacuum-packed food containers which will provide a means for relieving the vacuum within the container so as to provide a simple, fool proof, quick and easy solution to the problem of removing the container closure, yet will also address all storage, display, safety and consumer confidence issues.